README.md

June 27, 2026 · View on GitHub

ntn-slice

3GPP Network Slicing for Non-Terrestrial Networks: eMBB / URLLC / mMTC / V2X with GEO Mode-Skip Routing

Per-slice PRB orchestration for LEO + GEO non-terrestrial networks: eMBB / URLLC / mMTC / V2X slices with TS 22.261 demand profiles, per-slice latency / reliability KPIs, and a GEO mode-skip policy that keeps URLLC traffic off the orbital latency floor.

Part of ns3-ntn-toolkit — toolkit / INSTALL.

Overview

5G slicing is straightforward when every cell is a few kilometres away. In NTN the latency budget of a URLLC slice (5 ms p99) is hard-bounded by orbital geometry — a GEO leg adds ~120 ms of one-way slant propagation (~240 ms ground–satellite–ground), blowing the budget by more than an order of magnitude regardless of any radio-side allocator decision. ntn-slice is a 3GPP-compliant slicing layer that understands the orbital floor:

Per-slice PRB orchestration with min-throughput reservation, then priority-weighted distribution of the remainder by unmet demand — or by externally supplied RL shares. This orchestrator is an open-loop shadow allocator: its PRB decisions are computed and logged but do not actuate the mmwave scheduler. All slices share one slice-agnostic cell; the 5QI / S-NSSAI is a packet label the MAC never reads; and per-slice isolation is observed statistically on the measured plane, not enforced by the allocator. There is no per-slice isolation guarantee — the reservation is the allocator's own bookkeeping, not a scheduler-enforced PRB partition.
TS 22.261 demand profiles — default per-slice KPIs (latency budget, min/max throughput, reliability target, priority, allowGeo) seeded from TS 22.261 Table 7.1-1.
Per-slice latency / reliability KPIs — a rolling-window isolation monitor that emits a BreachEvent whenever a slice exceeds its p99-latency or loss-rate target.
GEO mode-skip policy — keeps URLLC traffic on LEO satellites whose round-trip time is compatible with the slice latency target; ShouldSkipGeo(slice) is true exactly for slices with allowGeo == false.

The orchestrator's (observation, action) shape matches the SliceEnv Gymnasium wrapper in ns3-ai, so a trained RL policy can drive the C++ allocator directly via StepWithShares().

Slice	SST	Default min throughput	Default latency budget	GEO allowed
eMBB	1	50 Mbps	50 ms	yes
URLLC	2	5 Mbps	5 ms	no — mode-skip
mMTC	3	1 Mbps	1 s	yes

The V2X SST enum value (SST 4) is defined, but no default V2X profile ships yet — only the three slices above have a default-profile factory.

What's new in v2

See the CHANGELOG for the full history.

All three examples now run on a measured radio. Every example builds a real mmwave NR NTN cell (NtnRealStackHelper from ntn-traffic: SpectrumPhy + MAC + RLC/PDCP + RRC + EPC) on a real SGP4 Walker satellite pass with TR 38.811 UE placement — no point-to-point stand-ins, no closed-form SNR curves.
Traffic is NtnOranApplication QoS flows (ntn-traffic), not OnOffApplication: each packet carries a real 24-byte in-band payload header (5QI / S-NSSAI / QFI / sequence number / TX timestamp), and per-UE delivered bytes are measured at the NtnOranSink. The MixedBouquet profile spreads UEs across eMBB (CBR-saturating, 5QI 2), URLLC (periodic pings, 5QI 82) and mMTC (periodic NB-IoT-style, 5QI 9) flows.
New ntn-slice-real-stack example: all slices contend for one shared mmwave cell, so per-slice service is genuinely contested rather than trivially separated by distinct links — but isolation here is measured on the shared cell, not enforced by a per-slice PRB scheduler (the orchestrator's PRB split does not drive the mmwave MAC).
ntn-slice-isolation-traffic was rebuilt on the same shared-cell recipe: the eMBB slice saturates the cell while URLLC and mMTC must hold their SLAs; per-slice SINR / throughput are measured and fed to the real SliceIsolationMonitor.
The three-slice LEO/GEO example validates URLLC GEO mode-skip against real geometry — LEO slant/c for LEO-served slices, the real ~36 000 km GEO slant/c (~120 ms one-way) for GEO-served ones — with delivery gated by the cell's measured TBLER.
served_mbps is clamped so it never exceeds the per-slice demand (no over-reporting of served load).

Models, helpers & key classes

Header	Provides
`model/ntn-slice-types.h`	`SliceSst` enum (eMBB / URLLC / mMTC / V2X); `Snssai` (8-bit SST + 24-bit SD with packed / unpacked codecs); `SliceProfile` (latency budget, min/max throughput, reliability target, priority, `allowGeo`); default profiles per TS 22.261 Table 7.1-1.
`model/ntn-slice-selector.h`	`NtnSliceSelector` — DSCP / port-range / app-label rule chain, first-match-wins, default fallback; maps a flow to its S-NSSAI.
`model/slice-orchestrator-xapp.h`	`SliceOrchestratorXapp` — PRB allocator with min-throughput reservation + priority-weighted unmet-demand sharing; `Step()` / `StepWithShares({snssai → fraction})` for RL override; `Tick` trace source exports per-slice allocated PRBs, served Mbps, satisfaction.
`model/slice-isolation-monitor.h`	`SliceIsolationMonitor` — rolling per-slice latency / loss-rate windows; `RecordPacket()` / `EvaluateAll()` returns `BreachEvent` records for latency-p99 and reliability breaches.
`helper/ntn-slice-helper.h`	`NtnSliceHelper::ThreeSliceDefault()` — ready-wired selector + orchestrator + monitor + the three default slices; GEO helpers `ShouldSkipGeo(slice)` and `IsGeoSatellite(altKm)` (altitudes at or above the conservative 30 000 km boundary are treated as GEO-class; GEO proper is 35 786 km).

A pre-built Grafana dashboard (dashboards/ntn-slice.json — per-slice satisfaction, served-vs-demand panels) can be imported into the Grafana stack that ships with the ntn-observability module.

Examples

Build all examples with ./ns3 configure --enable-examples --enable-tests && ./ns3 build. Each example produces the binary build/contrib/ntn-slice/examples/ns3.43-<name>-default.

ntn-three-slice-leo-geo

Three slices (eMBB / URLLC / mMTC) coexisting on a LEO + GEO NTN, with URLLC enforcing GEO mode-skip routing. The orchestrator runs at 1 Hz on top of a real mmwave NR cell (SGP4 LEO pass, TR 38.811 UEs): delivery is gated by the cell's measured TBLER, and per-slice latency is the real geometry — LEO slant/c for LEO-served slices, the ~36 000 km GEO slant/c (~120 ms one-way) for GEO-served ones — so the GEO-skip decision is validated against physics, not a hardcoded constant.

./ns3 run "ntn-three-slice-leo-geo --simTime=30 --csv=/tmp/three-slice.csv"

LD_LIBRARY_PATH=build/lib \
  ./build/contrib/ntn-slice/examples/ns3.43-ntn-three-slice-leo-geo-default \
  --simTime=30 --csv=/tmp/three-slice.csv

Outputs:

Per-slice KPI CSV at --csv (default ntn-three-slice.csv) — per tick: demand / served Mbps, allocated PRBs, satisfaction, p99 latency and latency / reliability breach flags per slice.
sim_health.csv in --outputDir (default ntn-three-slice-output), written by NtnRealStackHelper::WriteHealthReport().
Console summary: measured LEO SINR / TBLER, max URLLC p99 latency and breach counts.

Key args: --simTime (sim duration, s; default 30) · --numUes (UEs on the measured LEO cell; default 3) · --urllcViaGeo (force URLLC over GEO; gates the GEO-skip test) · --totalPrb (total PRB budget; default 273) · --satEirpDbm (LEO EIRP / gNB Tx power, dBm) · --csv (per-slice KPI CSV path) · --outputDir (output directory).

ntn-slice-isolation-traffic

Three slices share one real mmwave NR cell under genuine contention: the eMBB slice saturates the cell while URLLC and mMTC must hold their SLAs. UEs are assigned round-robin to slices (ue % 3) and carry NtnOranApplication per-slice traffic profiles (MixedBouquet). Per-slice SINR comes off the mmwave PHY trace, per-slice delivered bytes off the sinks, latency from the real slant geometry — all fed to the real SliceIsolationMonitor, which flags breaches.

./ns3 run "ntn-slice-isolation-traffic --simSeconds=15 --numUes=9"

LD_LIBRARY_PATH=build/lib \
  ./build/contrib/ntn-slice/examples/ns3.43-ntn-slice-isolation-traffic-default \
  --simSeconds=15 --numUes=9

Outputs: console isolation summary (measured cell SINR / TBLER / total throughput, per-slice measured throughput and SINR, SLA breach verdict under eMBB saturation) plus sim_health.csv in --outputDir (default ntn-slice-isolation-output) — nothing is hardcoded.

Key args: --simSeconds (sim duration, s; default 15) · --numUes (UEs on the shared cell, slice = ue % 3; default 9) · --satEirpDbm (satellite EIRP / gNB Tx power, dBm) · --backhaulMs (feeder + core one-way delay, ms) · --outputDir (output directory).

ntn-slice-real-stack

The shared-cell isolation recipe in its minimal form: all slices on one real mmwave cell, per-slice SINR and throughput measured from that cell, and the SliceIsolationMonitor evaluating SLA breaches against measured delivery plus the real geometric NTN latency — URLLC's 5 ms budget realistically breaches over the LEO slant while eMBB's 50 ms budget holds.

./ns3 run "ntn-slice-real-stack --duration=15 --numUes=9"

LD_LIBRARY_PATH=build/lib \
  ./build/contrib/ntn-slice/examples/ns3.43-ntn-slice-real-stack-default \
  --duration=15 --numUes=9

Outputs: per-slice measured throughput / SINR table, per-slice SLA breach evaluation on the console, and sim_health.csv in --outputDir (default ntn-slice-real-stack-output).

Key args: --duration (sim duration, s; default 15) · --numUes (UEs sharing the cell; default 9) · --altitude (satellite altitude, km; default 550) · --satEirpDbm (satellite EIRP, dBm) · --outputDir (output directory).

Build, run & test

./ns3 configure --enable-examples --enable-tests
./ns3 build
./test.py -s ntn-slice

The ntn-slice suite has 7 unit tests (S-NSSAI pack/unpack round-trip, selector first-match-wins, URLLC min-throughput preservation under contention, isolation-monitor breach detection, URLLC GEO mode-skip, three-slice co-existence, RL-shares honoured).

See INSTALL.md for setup and dependencies. For the full toolkit, see ns3-ntn-toolkit.

License & author

GPL-2.0-only — see LICENSE.

Muhammad Uzair, Independent Researcher.

@misc{uzair2026ntnslice,
  author = {Uzair, Muhammad},
  title  = {ntn-slice: 3GPP Network Slicing with GEO Mode-Skip for Non-Terrestrial Networks},
  year   = {2026},
  url    = {https://github.com/Muhammaduazir69/ntn-slice}
}

Scope & limitations (toolkit boundaries)

A4 — the per-slice PRB orchestration is computed and logged but does not actuate the (slice-agnostic) mmwave scheduler; isolation is observed statistically, not enforced. See the toolkit-wide SCOPE_AND_LIMITATIONS.md for the authoritative statement of what is and is not modelled.